1. Field of the Invention
The present invention relates to a display device, and more particularly, to a liquid crystal display (LCD) device and a method for driving the same.
2. Background of the Related Art
In general, electromagnetic interference (EMI) means that electromagnetic waves directly or indirectly emitted from electronic appliances generate problems in an electromagnetic receiving function of other electronic appliances.
With an increasing number of various electronic appliances and the development of digital and semiconductor technologies, the utilization of precision electronic appliances proliferates, thereby generating large quantities of electromagnetic waves. Such electromagnetic waves cause EMI, operational failures of electronic appliances, and biological hazards.
The EMI has been an issue in LCD components of display devices. Particularly, it becomes increasingly necessary to reduce the EMI in LCD devices because the EMI degrades the display quality that is one of the most important elements in the display.
In general, an LCD includes two glass substrates, and a liquid crystal layer between the two glass substrates. In a thin film transistor (TFT) LCD, the TFT serves as a switching device that applies a signal voltage to the liquid crystal layer. The TFT LCD has attracted attention as a display device to substitute for a cathode ray tube (CRT) due to the LCD's low power consumption and portability.
As shown in FIG. 1, the TFT-LCD includes a lower substrate 1 having the TFT serving as the switching device, and an upper substrate 2 has a color filter. A liquid crystal is injected between the lower and upper substrates 1 and 2. The TFT-LCD can display a picture image by manipulating the electro-optical characteristics of the liquid crystal.
As also shown in FIG. 1, a TFT array region 4 is formed on the lower glass substrate 1. Then, a black matrix film 5, the color filter 6, a common electrode 7, and an alignment film 8 are formed on the upper glass substrate 2.
The lower and upper glass substrates 1 and 2 are attached to each other by a sealant such as an epoxy resin. A driving circuit 11 on a printed circuit board (PCB) 10 is connected to the lower glass substrate 1 through a tape carrier package (TCP) 12.
In a timing controller of the above described LCD device, a data signal is synchronized with a data clock signal DCLK, and then is provided to a source driver.
A related art LCD device will be described with reference to the accompanying drawings.
FIG. 2 is a structure view of a related art LCD device.
As shown in FIG. 2, the related art LCD device includes an LCD panel 21, source drivers 23, gate drivers 25, and a timing controller 27.
The source drivers 23 apply data signals to the LCD panel 21, and the gate drivers 25 apply gate driving signals to the LCD panel 21. The timing controller 27 outputs power supply and control signals for controlling the source and gate drivers, makes clock signals CLK by receiving a data clock signal DCLK and digital data from a system (not shown), and outputs data synchronized with the clock signals CLK to the source drivers 23.
At this time, the timing controller 27 provides the digital data input from the system to each source driver 23 through data buses DB. The timing controller 27 simultaneously provides the clock signals CLK to each source driver 23.
The LCD panel 21 displays a picture image by controlling the source and gate drivers 23 and 25. The LCD panel 21 includes a plurality of gate and data lines that cross, and the TFT and a pixel electrode are formed at the crossing point of the data and gate lines.
The TFT includes a gate electrode formed on the lower glass substrate, a gate insulating film formed on an entire surface of the lower glass substrate including the gate electrode, a semiconductor film formed on the gate insulating film above the gate electrode, and source and drain electrodes formed on the semiconductor film (not shown).
Then, a passivation film is formed on the entire surface of the lower glass substrate including the drain electrode, and the pixel electrode is electrically connected to the drain electrode through a contact hole formed on the passivation film (not shown).
In general, the number of the source and gate drivers formed varies according to resolution. In a LCD panel of XGA (Extended graphics array) degree, eight source drivers 23 and three gate drivers 25 are required.
The source drivers 23 apply R/G/B (red/green/blue) data synchronized with the clock signals CLK applied from the timing controller 27 to each data line of the LCD panel 21.
The timing controller 27 outputs various control signals required to drive the source and gate drivers 23 and 25, and then provides data transmitted from the system (not shown) to the source drivers 23 at a rising edge timing of the clock signals CLK.
As shown in FIG. 3, the timing controller 27 provides R/G/B digital data to the source drivers 23 at the rising edge timing, and the source driver 23 samples the data at a falling edge timing of the clock signal CLK.
If the data is sampled within the source drivers 23 at the rising edge timing, the timing controller 27 provides the data to the source drivers 23 at the falling edge timing of the clock signal CLK.
Then, in the source driver 23, the digital data is converted to analog data, is constantly amplified, and then is applied to each gate line, thereby displaying the picture image by driving signals of the gate drivers.
However, the related art LCD device has the following problems.
First, the source driver connected with the data bus samples data per the falling edge timing of the data clock. At this time, unnecessary voltage is used, thereby increasing power consumption.
Furthermore, if the data is transmitted by an equal clock signal, an EMI noise emitted relatively increases, thereby degrading display quality.